I've actually heard a lot of people claiming it's roids that causes this. Bodies carrying around bulk that their frame simply wasn't meant to accommodate. End result, giant beasts with mad speed and power, how get hurt when their overstressed frames can't keep up. The same people that I've heard saying this often point to the days of leather helmets, or to sports like Rugby Union, where there are often huge pileups with minimal padding, minimal roids, and pretty few injuries.